zicntr is the Base Counters and Timers extension described in chapter 12
of the unprivileged spec. It describes support for RDCYCLE, RDTIME and
RDINSTRET.

QEMU already implements it way before it was a discrete extension.
zicntr is part of the RVA22 profile, so let's add it to QEMU to make the
future profile implementation flag complete.

Given than it represents an already existing feature, default it to
'true' for all CPUs. Accelerators are responsible for disabling them if
the user wants to.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c     | 12 ++++++++++++
 target/riscv/cpu_cfg.h |  1 +
 2 files changed, 13 insertions(+)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 2f98ce56e0..f478245254 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -79,6 +79,7 @@ const RISCVIsaExtData isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(zicbom, PRIV_VERSION_1_12_0, ext_zicbom),
     ISA_EXT_DATA_ENTRY(zicboz, PRIV_VERSION_1_12_0, ext_zicboz),
     ISA_EXT_DATA_ENTRY(zicond, PRIV_VERSION_1_12_0, ext_zicond),
+    ISA_EXT_DATA_ENTRY(zicntr, PRIV_VERSION_1_12_0, ext_zicntr),
     ISA_EXT_DATA_ENTRY(zicsr, PRIV_VERSION_1_10_0, ext_zicsr),
     ISA_EXT_DATA_ENTRY(zifencei, PRIV_VERSION_1_10_0, ext_zifencei),
     ISA_EXT_DATA_ENTRY(zihintntl, PRIV_VERSION_1_10_0, ext_zihintntl),
@@ -1175,6 +1176,15 @@ static void riscv_cpu_init(Object *obj)
     qdev_init_gpio_in(DEVICE(obj), riscv_cpu_set_irq,
                       IRQ_LOCAL_MAX + IRQ_LOCAL_GUEST_MAX);
 #endif /* CONFIG_USER_ONLY */
+
+    /*
+     * The timer and performance counters extensions were supported
+     * in QEMU before they were added as discrete extensions in the
+     * ISA. To keep compatibility we'll always default them to 'true'
+     * for all CPUs. Each accelerator will decide what to do when
+     * users disable them.
+     */
+    RISCV_CPU(obj)->cfg.ext_zicntr = true;
 }
 
 typedef struct misa_ext_info {
@@ -1263,6 +1273,8 @@ const RISCVCPUMultiExtConfig riscv_cpu_extensions[] = {
     MULTI_EXT_CFG_BOOL("svnapot", ext_svnapot, false),
     MULTI_EXT_CFG_BOOL("svpbmt", ext_svpbmt, false),
 
+    MULTI_EXT_CFG_BOOL("zicntr", ext_zicntr, true),
+
     MULTI_EXT_CFG_BOOL("zba", ext_zba, true),
     MULTI_EXT_CFG_BOOL("zbb", ext_zbb, true),
     MULTI_EXT_CFG_BOOL("zbc", ext_zbc, true),
diff --git a/target/riscv/cpu_cfg.h b/target/riscv/cpu_cfg.h
index 208cac1c7c..3c91b63609 100644
--- a/target/riscv/cpu_cfg.h
+++ b/target/riscv/cpu_cfg.h
@@ -62,6 +62,7 @@ struct RISCVCPUConfig {
     bool ext_zksh;
     bool ext_zkt;
     bool ext_zifencei;
+    bool ext_zicntr;
     bool ext_zicsr;
     bool ext_zicbom;
     bool ext_zicboz;
-- 
2.41.0